Noribogaine is a well known derivative of ibogaine and is sometimes referred to as 12-hydroxyibogaine. It is a metabolite of ibogaine. U.S. Pat. No. 2,813,873 claims noribogaine albeit as “12-O-demethylibogaine” while providing an incorrect structural formula for ibogaine. The structure of noribogaine has now been thoroughly evaluated and is found to combine the features of tyrptamine, tetrahydrohavaine and indolazepines. Noribogaine can be depicted by the following formula:

Noribogaine and its pharmaceutically acceptable salts have recently received significant attention as a non-addictive alkaloid useful in treating drug dependency (U.S. Pat. No. 6,348,456) and as a potent analgesic (U.S. Pat. No. 7,220,737).
Conventionally, noribogaine is prepared by demethylation of naturally occurring ibogaine:
which is isolated from Tabernanth iboga, a shrub of West Africa. Demethylation may be accomplished by conventional techniques such as by reaction with boron tribromide/methylene chloride at room temperature followed by conventional purification.
Ibogaine possesses hallucinogenic properties. It is a Schedule 1-controlled substance as provided by the US Food and Drug Administration. Accordingly, methods for preparing noribogaine from ibogaine require high levels of assurance that contamination with unacceptable levels of ibogaine is avoided. As above, a one-step method for preparation of noribogaine from ibogaine via demethylation does not provide the requisite assurance that ibogaine will consistently be removed as a potential contaminant.
Accordingly, there is an ongoing need to provide a method for preparing noribogaine from ibogaine wherein any ibogaine contamination of noribogaine can be effectively and repeatedly minimized.